The objective of this application is to upgrade the GE Omega NMR spectrometer of the NMR Laboratory for Physiological Chemistry with a Varian Associates UNITY INOVA. Specifically, the upgrade will replace all elements of the existing system (console, probes, room temperature shims, etc.) except for the magnet. The magnet will, however, be refurbished (de-energized, seals replaced, re-energized, field mapped, and supercon shimmed). The NMR Laboratory for Physiological Chemistry in the Cardiology Division of the Department of Medicine at Brigham and Women's Hospital currently supports ten NIH funded projects. These NIH projects are based at a number of institutions: the Brigham and Women's Hospital, the Beth Israel Deaconess Medical Center, and the Boston University School of Medicine. The NIH projects supported by the NMR Laboratory for Physiological Chemistry are primarily studying the isolated perfused mouse and rat heart. Other biological systems studied include intact rat and mouse leg, isolated cells, and extract samples. The rationale for upgrading the GE Omega NMR spectrometer, which is now ten years old, is to provide significant new capabilities to the supported projects and to provide a more reliable and available resource for the user community. The scientific aims of the current NIH funded projects demand a level of system performance that can not be met by the current system. This is especially evident in the studies of the isolated perfused mouse heart where the signal to noise and time resolution available in 31P NMR experiments is not adequate. The Varian UNITY INOVA console will have much improved signal to noise performance. Current noise figures for Varian system are at least 2 dB below those of GE Omega when it was new. In addition, ten years of hard use have degraded the performance of many critical components, in particular, the probes. Replacement of these old probes will also increase signal to noise. A second concern is the reliability of the GE Omega. Many critical components of the GE Omega system are no longer available. When breakdowns occur, parts must be sent out for repair or refurbishment. This is resulting in increasingly long periods of time when the instrument is unavailable for all studies. The great demand for instrument time and the time critical nature of many project studies (e.g., transgenic animals of a specific stage of development and exoerimenta1 models of hypertrophy) makes random and lengthy periods of unavailability very expensive and disruptive. The Varian UNITY INOVA will have vastly improved reliability and constant, predictable availability.